The invention relates to an oscillating piston machine, comprising a plurality of pistons which are arranged in a housing, rotate together in the housing about an axis of rotation which is essentially central in the housing and is fixed with respect to the housing, and execute reciprocating oscillating movements about a respective oscillation axis as they rotate in the housing, in each case two adjacent pistons executing oscillating movements in opposite directions.
Oscillating piston machines belong to a generic type of internal combustion engines in which the individual working strokes of the taking in, compression, ignition, expansion and expulsion of the combustion mixture are brought about by reciprocating oscillating movements of the individual pistons between two end positions.
The oscillating pistons rotate here in the housing about a common axis of rotation which is fixed with respect to the housing, the rotating movement of the pistons being converted by means of appropriate intermediate elements into a rotary movement of an output shaft. As the oscillating pistons rotate in the housing, they carry out the reciprocating oscillating movements.
In an oscillating piston machine known from WO 98/13583, the housing has a cylinder geometry on the inside. The pistons of the known oscillating piston machine are embodied as two-armed levers. In each case two adjacent pistons have a rolling engagement with one another. The pistons are each arranged so as to be capable of oscillating about a piston axis which is parallel with a central housing axis which lies on the cylinder axis. The piston axes extend in the direct vicinity of the inner wall of the housing, each piston having its own piston axis. In order to control the oscillating movements of the individual pistons as they rotate in the housing, a cam element which is central in the housing and fixed to the housing is provided, the individual pistons being guided along said cam element.
The individual working chambers which are formed in each case by two adjacent pistons are formed between sides of the pistons facing the inner wall of the housing and the inner wall of the housing.
Although the known oscillating piston machine has proven favorable in terms of its running properties and its torque curve, it can be considered to be a disadvantage of the known oscillating machine that the mass distribution of the pistons is capable of further optimization owing to the housing geometry and the fact that the individual pistons are borne on the inner wall of the housing.
Document U.S. Pat. No. 6,241,493 B1 has disclosed a device for controlling the flow of fluid through a rotation pump, a compressor or a motor. In a spherical housing a first blade rotates which causes at least one second blade to oscillate in a reciprocating fashion between alternately open and closed positions, to be precise the second blade moves away from the first blade and approaches it again in an oscillating movement. The fluid is moved through an inlet in the housing when the second blade approaches the closed position, while the fluid enters the housing when the second blade reaches the open position. One blade carries out a pure rotational movement and no oscillating movement while the other blade is capable of oscillation. This known device is accordingly based on a completely different working principle from that of the previously mentioned oscillating piston machine.
In addition, document DE 297 24 399 U1 discloses a device having at least two rotary pistons which rotate in an annular space and which bound, in their rotation direction, an expansion chamber in the annular space in the forward and backward directions, the rotary pistons being connected via a gearing arrangement to a common torque transmission shaft in such a way that the volume of the expansion chamber is alternately decreased and increased in the direction of rotation. The gearing arrangement has at least one bent cardan phase joint, which is not compensated in terms of its cyclical rotary displacement, between the torque transmission shaft and at least one of the two rotary pistons which bound an expansion chamber. In this known device, in each case two adjacent pistons approach one another and move away from one another by virtue of the fact that the pistons have varying rotational speeds as they rotate in the housing.